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Scientists have always been puzzled when it was carved and how it got so steep.

Now the mystery has been solved by Stuart Thomson, a geologist at the University of Arizona in Tucson, and a research team, whose findings were published in the March 2013 issue of the journal Nature Geoscience.

They tested samples of sands deposited by the river and rock piles pushed up by glaciers, and found the erosion rate more than doubled when the glaciers formed in Antarctica.

Bleak: The icy landscape of Antarctica which millions of years ago had a wide, lazy river running through it

Thomson said: 'People have speculated when the big
fjords formed under the ice, but no one knows for sure
until you sample the rocks or the sediments.'

The team examined layers of sediment offshore in Prydz Bay and decoded sands deposited by the river. They worked out the date and how quickly the surface eroded after tests on minerals in the sands.

Thomson concluded that from about 250
million to 34 million years ago, the region around Lambert Glacier was
relatively flat, and drained by slow-moving rivers.

About 34 million years ago - when
the Earth's climate cooled - big glaciers appeared, shaping the
spectacular valley now hidden under the ice.

The British study is the first to create a map of the Bedrock of the area

Some 5,250 to 8,200 feet (1.6 to 2.5
kilometres) of rock have since disappeared, ground down by glaciers and
carried away by the ice, says the study.

The research will help predictions of the ice sheet's response to future climate changes on the planet.

Thomson told OurAmazingPlanet: 'There's a big effort to model how glaciers flow in Antarctica, and these models need a landscape over which glaciers can flow.

'Once these models can predict past changes, they can more accurately predict what will happen with future climate changes.'